Tropical Storm KIKO

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TROPICAL STORM KIKO DISCUSSION NUMBER 12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152007
200 PM PDT WED OCT 17 2007
THE CLOUD PATTERN OF KIKO HAS BECOME RATHER DISORGANIZED THIS
AFTERNOON...WITH THE LOW-LEVEL CIRCULATION ELONGATED FROM
EAST-NORTHEAST TO WEST-SOUTHWEST AND THE CONVECTION DISPLACED TO
THE WEST BY 25 KT EASTERLY VERTICAL WIND SHEAR. OVERALL...THE
SYSTEM GIVES THE IMPRESSION OF BEING A SMALL LOW EMBEDDED IN THE
ITCZ OR MONSOON TROUGH. SATELLITE INTENSITY ESTIMATES ARE 45 KT
FROM TAFB AND SAB...BUT BASED ON THE RAGGED APPEARANCE THE INITIAL
INTENSITY WILL REMAIN 35 KT.
VISIBLE AND MICROWAVE IMAGERY INDICATES THAT THE CENTER IS FARTHER
EAST THAN PREVIOUS THOUGHT...SO THE INITIAL POSITION IS A
RE-LOCATION. THE INITIAL MOTION IS A RATHER UNCERTAIN 080/6.
KIKO IS SOUTH OF A BREAK IN THE MID-LEVEL SUBTROPICAL RIDGE CAUSED
BY A STRONG DEEP-LAYER TROUGH OVER THE CENTRAL UNITED STATES....AND
MUCH OF THE CURRENT MOTION MAY BE DUE TO LOW-LEVEL STEERING.
LARGE-SCALE MODELS FORECAST A MID-LEVEL RIDGE TO BUILD OVER
NORTHERN MEXICO BY 72 HR AS THE U.S. TROUGH MOVES EASTWARD. IN
THEORY...THIS SHOULD STOP THE CURRENT MOTION AND ALLOW KIKO TO TURN
GENERALLY NORTHWARD. WHILE MOST GUIDANCE SHOWS A NORTHWARD TURN IN
12 HR...THE BAMS AND ECMWF CONTINUE AN EASTWARD COMPONENT FOR 36 HR
OR MORE. AS A COMPROMISE BETWEEN THESE EXTREMES...THE NEW FORECAST
TRACK CALLS FOR 12 MORE HR OF EASTWARD MOTION FOLLOWED BY A SLOW
NORTHWARD MOTION. AFTER 72 HR...THE MEXICAN RIDGE WEAKENS AS A
SECOND DEEP-LAYER TROUGH MOVES INTO THE CENTRAL UNITED STATES. THE
MODELS REMAIN IN POOR AGREEMENT ON WHAT THE SECOND TROUGH WILL DO
TO KIKO. THE ECMWF AND NOGAPS HAVE A DEEPER TROUGH FARTHER
WEST...AND BRING KIKO NEAR OR OVER MAINLAND MEXICO. THE GFS AND
THE UKMET HAVE THE TROUGH FARTHER EAST AND RIDGING NORTHWEST OF
KIKO...AND TURN THE STORM WESTWARD AWAY FROM THE COAST. GIVEN THE
DISAGREEMENT...THE FORECAST TRACK CALLS FOR A SLOW NORTHWESTWARD
MOTION AFTER 72 HR. THE NEW FORECAST TRACK IS SHIFTED WELL TO THE
EAST OF THE PREVIOUS TRACK BASED ON THE CURRENT POSITION AND
MOTION. IT LIES WELL EAST OF THE MODEL CONSENSUS BUT WEST OF THE
ECMWF.
THE LARGE-SCALE MODELS FORECAST THE SHEAR TO DECREASE AFTER 24
HR...WITH GENERALLY FAVORABLE UPPER-LEVEL WINDS FORECAST BEYOND
THAT TIME. THIS SHOULD ALLOW SOME STRENGTHENING IF THE SYSTEM
DOESN'T LOSE ITS IDENTITY IN THE ITCZ BEFORE THEN. THE SHIPS AND
GFDL MODELS CALL FOR A 50-60 KT INTENSITY BY THE END OF THE
FORECAST PERIOD...WHILE HWRF CALLS FOR HURRICANE STRENGTH. THE
INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AS A
COMPROMISE BETWEEN THE SHIPS AND GFDL.
THE NEW FORECAST TRACK IS MUCH CLOSER TO THE SOUTHWESTERN COAST OF
MEXICO THAN THE PREVIOUS FORECAST...AND INTERESTS THERE SHOULD
MONITOR THE PROGRESS OF KIKO.
FORECAST POSITIONS AND MAX WINDS
INITIAL 17/2100Z 14.6N 105.4W 35 KT
12HR VT 18/0600Z 14.9N 104.7W 35 KT
24HR VT 18/1800Z 15.5N 104.7W 35 KT
36HR VT 19/0600Z 16.1N 104.8W 40 KT
48HR VT 19/1800Z 16.7N 105.0W 45 KT
72HR VT 20/1800Z 17.5N 105.5W 50 KT
96HR VT 21/1800Z 18.5N 106.0W 55 KT
120HR VT 22/1800Z 19.0N 106.5W 55 KT
$$
FORECASTER BEVEN
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